Detectives investigating the disappearance of a British sailor missing for more than 17 years are to return to Gibraltar to search for clues.
Simon Parkes was last seen in Gibraltar in December 1986
Simon Parkes from Kingswood, near Bristol, was a radio operator on the Portsmouth-based HMS Illustrious when he vanished in the colony in December 1986.
Hampshire Police re-opened the case in 2001 after his shipmate, petty officer Allan Grimson, was convicted of two murders back in Britain.
Three detectives from Hampshire and a naval police officer arrive in Gibraltar on Monday and will spend a week searching for clues.
One night in December 1986 the 18-year-old naval rating left his passport, belongings and Christmas presents on board the ship and visited a number of bars. He never returned.
Since then Hampshire Police and the Royal Gibraltar Police have carried out a number of searches on the peninsula.
Petty Officer Allan Grimson was convicted of two murders in 2001
Detective Inspector John Ashworth said: "We have carried out further research work and have made an assessment of the material that was gathered during our visit to Gibraltar in January.
"We have decided that there is now a need to carry out further searches in a specific area of the country."
He said the area to be searched during the week-long trip would not be identified.
In March 2001 Grimson was jailed for life at Winchester Crown Court for the murder of two men who were murdered in Portsmouth and dumped in the countryside nearby.
Sentencing him, Judge Peter Cresswell described Grimson as a "highly dangerous serial killer".
A month later police said they were investigating links between Grimson and Mr Parkes, who both served on the HMS Illustrious.
The Parkes family are desperate to know what has happened to their son
During the force's last visit to Gibraltar, dogs from the Netherlands National Police Agency Human Remains Detection Team were used to search the South Barracks and South Pavilion Road.
Det Insp Ashworth renewed his appeal for information about Mr Parkes' whereabouts to contact him.
"The Parkes family are desperate to know what has happened to their son," he said.
"They have lived with this situation for 16 years. Someone must know what happened to Simon and we would urge them to contact police with that information."